FILE - In this Sunday, June 8, 2003 file photo, a masked Chinese woman reacts as she stands in a crowd on the streets of Beijing, China. A genetic variant commonly found in Chinese people may help explain why some patients got seriously ill with swine flu, a discovery scientists say could help pinpoint why flu viruses hit some populations particularly hard and change how they're treated. Less than one percent of Caucasians are thought to have the gene alteration, which has previously been linked to severe influenza. About 25 percent of Chinese have the gene variant, which is also common in Japanese and Korean people. (AP Photo/Ng Han Guan, File)